Isometric View

View > Isometric

Right click > View > Isometric

Right click in the editor and select View > Isometric to view the model. The result should be similar to the illustration below.

In the illustration below, the Transparency option has been activated. Position the cursor over the model, right click and activate Transparency.

With the Extrude Solid tool still active, TAB to the Distance field and input a new Distance value of 15, making sure the dZ value is also set to 15.

Create a pick window around all the objects, shown below.

Using a pick window to select the objects for extrusion

The result is shown below.

Outer profile extruded